Uicollectionview custom layout pinterest

I want to reload the uicollectionview custom

dispatch_async(dispatch_get_main_queue(),{
collectionView.reloadData()
collectionView.layoutIfNeeded()
});

getting data from server and displaying in collection , loading 2 page , i cannot reload the collection view
can any one provide solution for this ?

What happens when that method is called?

Uicollectionview not reloading